Rocks are composed of one or more minerals, and can be classified into three main types: sedimentary, igneous, and metamorphic. Sedimentary rocks form from the compression of sediments like sand and pebbles, igneous rocks form from the cooling of magma or lava, and metamorphic rocks form from the alteration of existing rocks by heat, pressure, and chemical reactions. Some rocks like quartzite and granite contain multiple minerals, while others like gypsum and halite contain only one mineral.

2. What are rocks?
Classes of rock:
Most rocks are made up • Sedimentary
of more than one mineral. • Igneous
• Metamorphic
different mineral grains
granite
Some rocks are made up of
one mineral: monomineralic rocks.
quartz crystals
(mineral)
quartzite

3. Classes of rock:
What are rocks?
Most rocks are made up
• Sedimentary
of more than one mineral. • Igneous
different minerals • Metamorphic
joined together
Monomineralic rocks
Mineral Rock
granite
gypsum gypsum
halite rock salt
calcite limestone
quartzite